In recent years, some building codes have required new structures, for example, apartment houses, to include door closing devices on the entrance door of each housing unit. While in higher income units concealed hydraulic closing devices have been utilized, the requirements of the building codes can be satisfied by less expensive spring hinges.
Heretofore, spring hinges have been developed which meet the requirements of the building codes. A spring hinge is a hinge having within its tubular barrel a torsion spring which urges the door into a closed position. In U.S. Pat. No. 3,903,567 there is described a two knuckle spring hinge in which one end of the spring is non-rotatably supported by a capstan, which includes at least one radial cavity capable of being aligned with an aperture in a long hinge knuckle. A pin, adapted for insertion through the aperture and into the cavity, locks the capstan in place in the long hinge knuckle.
To adjust the torsion of the spring, the pin must be removed from the cavity and the capstan rotated. When the pin is removed, the capstan tends to be forced out of the long hinge knuckle by the spring, thereby necessitating axial as well as circumferential alignment of the cavity and aperture. Thus, in order to insert the pin through the aperture into the cavity, the capstan must be rotated and manually restrained from being pushed axially out of the long hinge knuckle.
The length of the pin is equal to the combined length of the cavity and aperture so that the pin does not extend externally of the long hinge knuckle. Although, in the past, spring hinges have utilized longer pins which extend outwardly from the hinge knuckles, those pins are disadvantageous because they detract from the aesthetic appearance of the hinge. On the other hand, the utilization of longer pins is advantageous, inasmuch as they are easier to insert and remove.